Growth of concentrated GaInSb alloys with improved chemical homogeneity at low and variable pulling rates

Crystal growth of concentrated GaInSb alloys during vertical Bridgman method has been numerically and experimentally investigated. The numerical and experimental results show a strong solutal damping effect on the melt convection in the case of concentrated (x=0.1 and 0.2) alloys grown at 1 μm/s pulling rate of the crucible. This leads to a huge increase of chemical heterogeneities and solid-liquid interface curvature. Analytical relations, which describe the solutal effect on the melt convection, show that the damping effect can be avoided by using low growth rates. The experimental results for Bridgman solidification of Ga0.85In0.15Sb at V=0.4 μm/s pulling rate, show that the axial and radial variations of indium concentration in the sample are reduced as compared with crystals grown at high pulling rates. The interface deflection is maintained at lower values during the growth process and the morphological destabilization of the interface occurs only at the end of the solidification. The growth at variable pulling rates is also investigated and from the numerical modeling it is found that the axial chemical homogeneity of the sample can be improved.